Milky Way ‘larger than imagined’

January 6, 2009

The Milky Way is considerably larger, bulkier and spinning faster than astronomers thought, it has been revealed.

For decades, stargazers thought when it came to the major neighbouring galaxies, our Milky Way – home to Earth – was a weak sister to the larger Andromeda, but not anymore.

Scientists mapped the Milky Way in a more detailed, three-dimensional way and found that it is 15% larger in breadth. More important, it is denser, with 50% more mass, which is like weight.

The new findings were presented at the American Astronomical Society’s convention in Long Beach, California.

Mark Reid of the Harvard-Smithsonian Centre for Astrophysics in Cambridge, Massachusetts, said it was the cosmic equivalent of him suddenly bulking from his 5ft 5in, 10 stone frame, to 6ft 3in and 15 stone.

“Previously we thought Andromeda was dominant, and that we were the little sister of Andromeda,” Mr Reid said. “But now it’s more like we’re fraternal twins.”

That is not necessarily good news. A bigger Milky Way means that it could be crashing violently into the neighbouring Andromeda galaxy sooner than predicted – though still billions of years from now.

Mr Reid and his colleagues used a large system of 10 radio telescope antennas to measure the brightest newborn stars in the galaxy at different times in Earth’s orbit around the sun.

They made a map of those stars, not just in the locations where they were first seen, but in the third dimension of time – something Mr Reid said has not been done before.

With that, Mr Reid was able to determine the speed at which the spiral-shaped Milky Way is spinning around its centre. That speed – about 568,000mph – is faster than the 492,000mph that scientists had been using for decades.